Can I extend in a conservation area or under an Article 4 direction?

Householder permitted development comes from the General Permitted Development Order 2015, Schedule 2, Part 1. A conservation area is "article 2(3) land" under that order, and the order withdraws some rights there. The rest stay, with the same limits as anywhere else.

The table sets out the usual London jobs. "Normally permitted development" still means every limit has to be met: depth, height, eaves near a boundary, half the garden, and materials of similar appearance (GPDO 2015 Sch. 2 Pt 1 A.3(a)). Everything is measured against the original house, so earlier extensions count.

For a loft, the difference is large. Class B, which covers dormers and hip-to-gable conversions, does not apply in a conservation area at all (GPDO 2015 Sch. 2 Pt 1 B.1(f)), so even a modest rear dormer needs an application. Rooflights that sit close to the slope remain permitted under Class C, which is why a rooflight loft is the usual way to convert without an application in a conservation area. A mansard needs an application almost anywhere, because it changes the roof slope that faces the street and rarely fits the volume and height limits.

An Article 4 direction is an order a council makes to remove particular permitted development rights in a defined area. Where it applies, the work it names needs a planning application even if it would otherwise be permitted. Councils often make them inside conservation areas to protect front windows, doors, roofs and boundary walls, but a direction can cover any area the council chooses.

Many London directions have nothing to do with householder work. A large share concern turning a family house into a small house in multiple occupation, or turning shops and offices into homes. Those remove rights under other parts of the order and leave your extension or loft exactly where it was. Only a direction that removes rights under Part 1, the householder part, affects an extension, a dormer or rooflights.

To tell, read the direction itself. It lists the classes of development it removes, in words such as "Schedule 2, Part 1, Class A" for extensions or "Class B" for roof additions, and it has a map of the streets it covers. The council's Article 4 page usually links each direction with a short summary. If the wording is unclear, check with the council.

Every London borough has conservation areas, and they range from a few streets to whole districts. The government's planning data service, planning.data.gov.uk, publishes conservation area boundaries and Article 4 directions for the councils that supply them, with the rights each direction removes where the council records it.

Our borough pages list what open data holds for each borough: the conservation areas recorded, and the Article 4 directions that affect householder permitted development rights. Coverage is partial: a miss means none found in open data, not none designated. Some councils publish only part of their registers, and Article 4 data covers about half of London's boroughs. The full report checks the exact address against these registers and says which result came from which source.

Confirm the constraint first. The council's conservation area map and its Article 4 page settle whether your house is covered. The report screens the address, but the council's records are the final word.

Read the council's appraisal for your conservation area. Most councils publish one, describing what gives the area its character and which changes it resists, such as roof additions visible from the street or the loss of original windows. Rear extensions out of public view are usually treated more flexibly than anything at the front.

Ask for pre-application advice. Most London councils run a paid service where a planning officer, and sometimes a conservation officer, comments on a sketch scheme before you apply. It costs time and a fee set by each council, and it is the best guide to what the council will accept.

Prepare a heritage statement. An application in a conservation area should explain what is special about the area and how the design respects it. A short statement with photographs of the house and street is normally enough for a rear extension or dormer; your designer or planning consultant can write it.

Match the materials. Brick, roof covering, windows and detailing that match the house, or a deliberately contrasting design that is well argued, carry more weight in a conservation area than anywhere else.

For the parts that remain permitted, such as a single-storey rear extension within the limits or rooflights, apply for a lawful development certificate. The council fee is £274, and it gives you the council's written confirmation before you build.

The building work itself costs much the same per square metre, but a few things add to the total. Design takes longer, because the drawings need more detail and often a second round after the council's comments. A heritage statement and pre-application advice add fees. Matching materials can cost more than standard ones: reclaimed or matched brick, natural slate, and timber sash or casement windows instead of uPVC.

The planning application is the main fixed cost: the council fee of £548, plus the Planning Portal charge of £85 if you apply through the portal. The council has eight weeks to decide a householder application, and in a conservation area it is common for the decision to take longer. Whether an application needed only because of an Article 4 direction carries a fee is a question to put to the council. The report adds these lines to the estimate for your address.

Can I build a loft conversion in a conservation area?

Often, yes, but a dormer or hip-to-gable needs a planning application, because Class B does not apply in a conservation area (GPDO 2015 Sch. 2 Pt 1 B.1(f)). The council fee is £548. Rooflights that project no more than 0.15 m remain normally permitted development, subject to the limits checked in the report. Councils tend to accept rear dormers out of view from the street more readily than anything on the front slope; check with the council.

How do I find out if my house is in a conservation area or under an Article 4 direction?

Look up your address on the council's conservation area map and its Article 4 page, and read the wording of any direction that covers your street. The borough pages here show what open data holds for each borough, and the full report checks the exact address. A miss in open data means none found, not none designated, so check with the council.

Does an Article 4 direction mean my extension will be refused?

No. A direction removes the automatic right to build; it does not ban the work. Where it removes Part 1 rights, the extension needs a planning application, which the council decides on its merits like any other. Many London directions concern houses in multiple occupation or shops and do not touch householder work at all.